Is that 4 inch, or 4 foot ?
My coffee cup is about 4 inch !
I hope you mean the larger size, also that you have filter & heater etc. and cycled the tank so it can deal with fish waste.
Lot's of threads here about how to get your water condition right. Homedog... your guidance methinks !!
In the beginning, there was this enormous bang..... and then the world was formed !